1. Field of the Invention
The present invention relates to a liquid ejection head.
2. Description of the Related Art
An ink jet recording head used in an ink jet recording apparatus has heretofore been provided with a recording element substrate in which an ejection orifice group for ejecting an ink has been formed, a support member for holding and fixing the recording element substrate and an electrical wiring substrate having a lead terminal group connected to a connection terminal group of the recording element substrate. The connection terminal group provided in the recording element substrate and the lead terminal group provided protruding from the electrical wiring substrate make up an electrical connection portion.
The recording element substrate is held and fixed to the support member through an adhesive. A peripheral portion of the recording element substrate and the electrical connection portion are sealed with a sealing material for preventing connection failure such as corrosion caused by an ink and disconnection caused by external force. In the neighborhood of the electrical connection portion, for example, the peripheral portion of the recording element substrate is coated with a sealing material, a lower space of the lead terminal group is sealed with the sealing material, and the electrical connection portion including the lead terminal group is then coated with the sealing material. As the sealing material, is generally used a thermosetting resin that is relatively easy to be handled in a production process.
The ink jet recording head is subjected to a printing test before shipment, and ink droplets attached to the surface of the recording element substrate are then washed out. The surface of the recording element substrate is then dried, and a tape coated with a pressure-sensitive adhesive is lastly applied on the surface of the recording element substrate for preventing ink leakage from the ejection orifice upon physical distribution.
When a washing solution is left on the recording element substrate after the washing and drying steps, the remaining washing solution may fly off by vibration during transfer to the next step and re-applied to the surface of the recording element substrate in some cases. When the tape is applied on the surface of the recording element substrate in this state, ink bleeding or color mixing may be caused in some cases.
As a countermeasure against this, Japanese Patent Application Laid-Open No. 2006-239992 has proposed such a construction that ribs are respectively provided on three surfaces of a periphery of an electrical wiring substrate arranged in a support member except for a surface opposing a contact portion with an ink jet recording apparatus, and a groove is formed in a rib most distant from the contact portion among these ribs. The groove is a notch provided so as to open a part of the rib. The washing solution can be discharged to the outside through the groove provided in the rib opposing the contact portion in the drying step after the washing step to prevent the washing solution from flying off from the surface of the recording element substrate and being re-applied thereto.
In recent years, there has been a demand for providing in the market an ink jet recording head that is cheaper while retaining high recording quality. In order to reply to this demand, it is necessary to extremely diminish the size of the recording element substrate that is the most expensive in the ink jet recording head and to increase the number of recording element substrates producible from one wafer. However, when the size of the recording element substrate is diminished, a wall portion around an ejection orifice inevitably becomes fine, and the rigidity of the recording element substrate is lowered. Therefore, the recording element substrate is liable to be deformed or broken by slight force.
An ink jet recording head is subjected to a heat treatment for curing the sealing material after the sealing step. Since the curing temperature of the sealing material is higher than room temperature, the sealing material is cured and shrunk before returned to room temperature to restrain the recording element substrate. A resin material is generally used in the support member due to the advantage that it can be cheaply produced, and the recording element substrate is mainly formed with a silicon material, so that both are different from each other in coefficient of thermal expansion. Upon sealing, the recording element substrate and the support member become a more expanded state than those at room temperature, so that a difference in thermal expansion between the recording element substrate and the support member is created to mutually restrain them through the sealing material after the curing.
As a result, the internal stress of the recording element substrate may have been increased in some cases to deform the recording element substrate. An ink ejected from an ink jet recording head having the recording element substrate deformed as described above changes its ejecting direction, so that its impact position is dislocated to cause lowering of recording quality. Thus, it is considered that sealing of a portion, on which no electrical connection portion is provided, of the recording element substrate is omitted or simplified to reduce the restraining force of the sealing material.
On the other hand, it is desirable to provide a groove around a joint portion for joining the recording element substrate to the support member. By providing the groove, a meniscus is formed upon coating of an adhesive to stabilize the coating height of the adhesive. However, the groove remains along a peripheral portion of the recording element substrate when the sealing material is not provided after the joint. When the washing solution enters this groove portion in the washing step after the printing test, it is difficult to remove the washing solution in the next drying step. When being transferred to the next step while the washing solution remains in the groove portion, the washing solution flies off by vibration upon the transfer and re-applied to the surface of the recording element substrate to cause ink bleeding or color mixing upon application of the tape.
The groove described in Japanese Patent Application Laid-Open No. 2006-239992 is useful to discharge water on the recording element substrate and the electrical wiring substrate. However, it is difficult to effectively discharge the washing solution remaining in the groove portion in the neighborhood of the joint portion of the recording element substrate.